Do you have a photo of the insects you are wondering about? A identification cannot be made from a description.

If you would like information on growing coriander seed you can review this article.

https://hort.extension.wisc.edu/articles/cilantro-coriander-coriandrum-sativum/

There are known infestations of Chalcid wasp, a tiny benificial wasp, in coriander. Some research I have found show the larve can be killed by liquid nitrogen. Even if this is an insect you have this is likely beyond the scope of a home gardener. As with any product, if there is a question of safety it is better to err on the side of caution.